Although Cicero defended human freedom against the determinism of the Stoics, he attacked the randomness implicit in the Epicurean swerve of the atoms. He put the attack into the mouth of his Academic philosopher Cotta, criticizing the Epicurean Velleius, in Book I, section XXV, paragraphs 69 and 70 of De Natura Deorum.

(69) XXV. "This is a very common practice with your school. You advance a paradox, and then, when you want to escape censure, you adduce in support of it some absolute impossibility; so that you would have done better to abandon the point in dispute rather than to offer so shameless a defence. For instance, Epicurus saw that if the atoms travelled downwards by their own weight; we should have no freedom of the will [nihil fore in nostra potestate], since the motion of the atoms would be determined by necessity. He therefore invented a device to escape from determinism (the point had apparently escaped the notice of Democritus): he said that the atom while travelling vertically downward by the force of gravity makes a very slight swerve to one side. (70) This defence discredits him more than if he had had to abandon his original position. (Loeb Classical Library translation, v.40, p.67)

This appears to be the first appearance of the standard argument against free will. Notice that it already appears in the form of a logical proposition, one or the other of determinism or randomness must be true.

(70) XXV. "He does the same in his battle with the logicians. Their accepted doctrine is that in every disjunctive proposition of the form' so-and-so either is or is not,' one of the two alternatives must be true. Epicurus took alarm; if such a proposition as 'Epicurus either will or will not be alive to-morrow' were granted, one or other alternative would be necessary. Accordingly he denied the necessity of a disjunctive proposition altogether. Now what could be stupider than that?
(Loeb Classical Library translation, v.40, p.67)

Cicero wanted to eliminate the causal determinism implicit in the Stoic doctrine of divine foreknowledge.

"If there is free will, all things do not happen according to fate; if all things do not happen according to fate, there is not a certain order of causes; and if there is not a certain order of causes, neither is there a certain order of things foreknown by God."

The irony is that Epicurus had the same goal. His swerve was simply to deny the causal chain of strict Democritean determinism, while also preserving human autonomy from intervention by the gods.

So Cicero, blinded perhaps by his distaste for Epicurean philosophy, and perhaps because Lucretius connected the swerve too closely with human freedom and will, misled philosophers for centuries who argue that Epicurean free will involves chance directly in the decision, that for every free action there is a swerve of the atoms in the mind - "one swerve = one decision."

This is the same mistake as trying to identify a single quantum event in the brain as responsible for a free action.

Epicurus himself distinguished free human actions, for which an agent can be morally responsible, from those fated by necessity or randomly caused by chance:

...some things happen of necessity, others by chance, others through our own agency. ...necessity destroys responsibility and chance is inconstant; whereas our own actions are autonomous, and it is to them that praise and blame naturally attach. (Letter to Menoeceus)